It’s been a relatively quiet six months at the bridge since we last reported on it.  LBHF announced the award of a 9-month stabilisation contract to deal with cracks in the cast-iron pedestals, at a cost of £8.9m, and there’s been some to-ing and fro-ing on who’ll pay (finally equally split LBHF, TfL, DfT), setting aside the cost of the future major repairs necessary, still undecided.  The stabilisation will enable the main repair and renewal of other components of the bridge to follow in a separate contract.

During the stabilisation contract cyclists will not be allowed on the main carriageway but must wheel their bikes on the walkway – hoardings have gone up to that effect, though social media suggests that the dismounting instructions have yet to reach all quarters!

We noted late last year that the council had observed planning niceties by applying to itself for permission for the stabilisation works under ref 2021/03680/LBCHF. which it formally approved at the end of February. We understand similar has happened on the South side with LBRUT.  Subsequently, an application has been lodged for temporary removal of sections of the handrail to allow pedestrians/cyclists to still cross while bypassing the pedestal housings, under 2022/00786/DLBC. 

Engineering

Concrete infill from 2021/03680/LBCHF

We remain a little disappointed that the plan still involves pouring concrete into the now infamous cast iron pedestals – not recognised bedfellows – but this is an old comment that has so far been met with a tin ear. We must hope the thermal effects and regular bridge vibration which have been written about at length, and even reported by a concerned member of the public last week, don’t gradually separate or crumble this unusual mixture. If it was a recognised and tested process, a standard method statement would be referenced, but instead the designer has listed an array of materials and notes on the drawings, the word “suitable” signposting a degree of conjecture.  We can find no risk assessment to cover the effect of the additional mass, in the light of concerns about the strength of the pedestal footings noted during earlier investigations. The figure mentioned was 6 tonnes per pedestal, and it would be sensible to properly address this risk.

The documents state that Historic England is satisfied that the proposal respects Bazalgette’s design because the pedestals are not visible, which was precisely the point we made last year. If invisible, then remove them and do the job properly as a self-respecting engineer such as Bazalgette would do, having recognised a design or material weakness, and with the existence of better modern materials. Replacing them with something stronger, lighter, maintainable, and built offsite, allowing a quick like-for-like replacement (12 bolts), and future bearing maintenance, without all the onsite paraphernalia and disruption now planned, is the right thing to do, and also cheaper – especially long-term.  The existing plan falls into the unfortunate category of being neither fish nor foul – not comprehensive enough to improve function, future maintenance and de-risk the structure, not quick or cheap enough to say it’s a disposable fix until major repairs can be undertaken.

Repair and Renewal

The  repair and renewal contract involves replacing 172 hangers, repairing the bearings at the top of the four towers and dealing with defects in many other components to restore the bridge to its former glory, strength and usefulness.  There are two options for providing a temporary crossing for the public during this repair work:

• 

  Foster & Partners bridge proposal

  The Foster scheme on which we reported last year, involving a ’tube’ structure within the Heritage bridge passing between the towers and allowing the progressive replacement of bridge sections and components.

• The Beckett Rankine scheme involving a 5-span crossing adjacent to the Heritage bridge.

The Foster scheme is daring and brilliant and might provide the best of all worlds, but there are considerable technical uncertainties and perhaps no contractor would be prepared to undertake the work. New Civil Engineer recently reported that the council has agreed to fund a feasibility study to address this uncertainty.

The Beckett Rankine scheme appears technically straight-forward but adjacent occupiers might cause unacceptable delay and frustrate the scheme.  There is seldom space available for a temporary bridge and its approach roads to be aligned beside it. 

Beckett Rankine bridge bypass proposal

But in the case of the Hammersmith Bridge, it’s been suggested that there’s space available alongside Digby mansions, though we understand from our affiliate HAMRA, that residents refute this for several reasons. The alternative is at Queen’s Wharf/Queen Caroline St. on the Eastern side.  The scheme that Beckett Rankine eventually drew up after consideration of all the issues, shown adjacent, consequently landed at Queen Caroline St.  Viability was then seriously considered by TfL and still found wanting, leaving just the Foster scheme and its current feasibility study.

Repairing the bridge without providing a temporary crossing facility would be disappointing and disruptive for communities on each side of the bridge, and indeed for many others in southwest London who would suffer years of congestion and its related pollution. The repair would also take longer and be substantially more expensive than if the contractor had some use of the temporary structure for access.

It is no secret that the bridge has become a battleground between LBHF and the Department for Transport. DfT have proposed the cost should be shared three ways equally with TfL and LBHF.  It is believed that TfL have accepted this but LBHF have not, as we reported last time.

A recent DfT update stated: ‘DfT continues to assist LBHF.. .but there are significant elements of the project where further input from DfT is dependent on LBHF addressing the very substantial gaps in the information supplied so far.’  The bridge report from Sarah Olney MP at the end of January stated that a business case had not been submitted to the Department for Transport by LBHF, but we’ve just been told this has now been completed, and we await the details.  A contemporaneous ITV news story captures the key issues and protagonists.

Decisions on the way ahead involve a great deal of hard work for LBHF; but this may present them with an opportunity to show wisdom and leadership.

With thanks to Edmund Sixsmith for his contributions